Mil-Dots Explained

Discussion in 'Technical Questions & Information' started by CountryGunsmith, Feb 24, 2003.

  1. CountryGunsmith

    CountryGunsmith New Member

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    green275
    Member
    Posts: 3
    (9/21/02 11:09:23 pm)
    Reply | Edit | Del All Help with mil dot use please....
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    I have seen a tasco "varmint" scope in perfect condition that I plan to get for a 10/22. It is 2.5-10x42. It also has mil dots on the reticle. I read quite a bit on the www about the mil dot system, and I think I understand their use, except for a couple things.... Is it assumed, when using the scales or tables, that you have sighted your rifle in at 100 yards? Do you have to have a 1 minute gun, or do the tables still work if your groups are not that tight?

    These are the Army mil dots (round).

    Also, how does adjusting the magnification on the scope affect the use of the tables?

    And, just generally, does anyone know what this scope should be worth, and should I buy it, knowing tasco is gonzo?

    Thanks for the help!

    Edited by: green275 at: 9/22/02 12:35:00 am

    Zigzag2
    *TFF Senior Staff*
    Posts: 4243
    (9/22/02 8:35:33 am)
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    check this out www.eabco.com/mildot01.htm
    In this age where truth is fleeting and mass manipulation is common, the ability to detect when something doesn't make sense is a valuable one.


    green275
    Member
    Posts: 4
    (9/22/02 5:57:11 pm)
    Reply | Edit | Del Re: Help with mil dot use please....
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    Thanks, ...I think I've read just about every article on mil dots on the web... but I can't find where any of them state what magnification the base calculations begin at, or how increaseing/decreasing magnification affects the math. It's probably something obvious, (such as; it makes no difference what magnification) but I am looking for confirmation of something like that.

    Any takers?

    CaliCollector
    V.I.P. Member
    Posts: 61
    (9/22/02 9:41:45 pm)
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    ezSupporter
    Re: Help with mil dot use please....
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    there was a very good article in a rifle magazine last month, it was about the owner of a ammunition company.. big name small outfit, cant remember the name.. but he also doubles as a sniper for the local law enforcment agency... had good tidbits on range estimation and doing the math with a mil-dot scope... i have to find it.. but as soon as i do.. ill post it, i thought it was well written.. heck i understood it..lol.. so it had to be ....Ray in California
    "Beware the man with only one gun, chances are he KNOWS how to use it."

    green275
    Member
    Posts: 6
    (9/22/02 11:11:39 pm)
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    Looking forward to seeing that post, thanks.

    Any other expertise out there would be greatly appreciated!

    CaliCollector
    V.I.P. Member
    Posts: 63
    (9/23/02 3:02:22 am)
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    ezSupporter
    Re: Help with mil dot use please....
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    what follows is a quote from an article that was printed in GUNS Magazine 2003 Annual, pg 59 "Long Range Shooting- A Professional's Approach" by Dave Anderson... article is about Jeff Hoffman president and co-owner of Black Hills Ammunition, and techniques he uses to obtain 800 yard shots consistantly.... the part on Mil-Dots is as follows....

    pg. 62

    "....Mil-dot reticles have a series of dots precisely placed so that the spacing from the center of one dot to the center of the next subtends one mil. A "mil" (short for milliradian) is one unit of distance per 1,000 units; for example one yard at 1,000 yards, one meter at 1,000 meters.
    If target size is known, a skilled operatorcan use the dots to estimatedistance with considerable accuracy. The mathematical formula for finding range in yards is: size of target(in yards) times 1,000 divided by the size of the target in mils.
    Lets try a simple example from a sporting perspective. Adult buck mule deer supposedly average 18 inches from top to bottom at the chest. Lets presume the buck is obliging enough to pose broadside, long enough for us to get a solid rest for the rifle.We lay the horizontal crosswire along the bottom edge of the body and find that the center of the next dot is exactly on the line of the back. We therefore read the target size in mils as exactly one mil.
    Turning to the formula ,target size in yards is half a yard(18 divided by 36= .5 yards). Multiply .5 yards by 1,000 and we get 500, and dividing by one (the target size in mils) we arrive at a range estimate of 500 yards." break quote

    i think this first example is easiest to understand, least it was for me....

    resume quote
    "Theres another formula that many find more convenient. We've said that a mil is one unit per 1,000 units of distance. That means a mils is also one inch at 1,000 inches. 1,000 inches is 27.78 yards( rounded to two decimal places). If one inch is 27.78 yards, and the target is 18 inches in size, we can multiply 27.78 yards by 18 inches , divide by the mil-dot reading(one, in this example), and the result will be 500 yards.
    Thats simple enough, but suppose the game is a pronghorn antelope and we assume that it measures 15 inches in depth. It fills less than one mil-dot spacing. Estimating as carefully as we can, we decide that it covers 9/10 of a spacing (.9 mil). Quick do the math; 15 divided by 36 times 1,000 divided by 0.9. Better hurry, the buck is getting fidgety out there. It would take me some considerable time to figure it out without a calculator wich i just did - 463 yards.
    In reality we won't likely be punching calculator buttons while the game patiently waits. We could make up a chart based on a target size of 18 inches, showing the range for each mil reading. With practice and a steady rest most shooters can learn to make mil readings to teh first decimal place. our chart might look like this:

    MIL DOT READING RANGE IN YARDS
    18 INCH TARGET
    0.8 625
    0.9 556
    1.0 500
    1.1 455
    1.2 417

    Even with charts, mil-dot ranging has practical problems in big game hunting. Animals seldom stand around in the right positon, patiently waiting. Nor do tehy come off an assembly line. In the first example , the range estimate of 500 yards assumes that the buck is 18 inches in depth. Suppose it is larger than average, actually measuring 20 inches deep. This means that instead of the 500 yards we've estimated the deer is actually 555.5 yards away. At that range the bullet is on the down slop of the trajectory curve - if we hold for 500 yards the bullet may likely miss low, or worse yet break a leg.
    Police and military marksmen operating in an urban enviroment have teh advantage of a sea of objects of known size. They'll know, or have recorded in their rrange books , examples such as the dimensions od a standard door, the width of a mailbox, the height of a stop sign or yield sign. In hunting fields we do not have the standard of comparison. The only objects of known size are the animals themselves, and they cant be trusted." end quote

    personally i found the first example of using the Mil-Dot system easier to understand, but thats only because there was less numbers stated in the article... and im not the brightest bunny in the woods... hope this helps... and since i did not see anything in the article or magazine that said anything against forwarding the info along, least the pertinant parts... i hope my judgement was correct in sharing it... id suggest buying the Guns Magazine 2003 Annual and reading the whole article myself though the cost is $9.95 U.S. and outside the U.S. $12.95...
    also i hope no one on the forum minds my using this info i obtained from a magazine in this manner.. if anyone does, please delete my post... also if this in ANYWAY endangers TFF or anyone else, DELETE IT IMMEDIATLY PLEASE!!!!!!!!

    Ray in California
    "Beware the man with only one gun, chances are he KNOWS how to use it."

    green275
    Member
    Posts: 7
    (9/23/02 8:35:01 am)
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    Thats a great article, and the first part was easiest for me too; Thanks for posting. but I'm still not sure what magnification it is assumed you begin using, or how/if changing magnification alters the basic formula. (Maybe it doesn't?)

    Keep those post coming!.... I'm soaking it all up as fast as I can!

    Zigzag2
    *TFF Senior Staff*
    Posts: 4255
    (9/23/02 8:48:07 am)
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    Thanks Ray for taking the time and energy to make such a post.

    It's well received and appreciated both from myself and TFF.
    In this age where truth is fleeting and mass manipulation is common, the ability to detect when something doesn't make sense is a valuable one.


    AntiqueDr
    *TFF Senior Staff*
    Posts: 3117
    (9/23/02 10:17:05 am)
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    ezSupporter
    Re: Help with mil dot use please....
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    Sorry I'm late.

    Yes, magnification affects the mil-dot. In scopes where the reticle does not change size with magnification, the mil-dot is calibrated to subtend one milliradian at the maximum magnification of the scope. In most military configurations, this is 10x. To extrapolate the distance at any other magnification, you must divide the current magnification into the maximum calibration to determine the fraction.

    I must take this opportunity to point out that there is one scope manufacturer that renders this obsolete - Shepherd.


    We Buy Guns! 1 - 100, Antique or Modern!
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    CaliCollector
    V.I.P. Member
    Posts: 64
    (9/24/02 6:00:14 am)
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    ezSupporter
    Re: Help with mil dot use please....
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    Green and ZigZag, im just happy that i may have been able to help in a small way... Ray in California
    "Beware the man with only one gun, chances are he KNOWS how to use it."

    green275
    Member
    Posts: 9
    (9/24/02 8:23:14 am)
    Reply | Edit | Del Re: Help with mil dot use please....
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    Cali, antique, and all others;

    Thanks a thousand times for the info! you guys are great.
    I don't know what we newbies would do without y'all.
     
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